Fix CI: Clean workspace before clone

- Add rm -rf /opt/gbo/data/botserver before git clone
- Prevents 'destination already exists' error on re-runs

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

.forgejo/workflows/botserver.yaml

@@ -28,6 +28,8 @@ jobs:
         run: |
           mkdir -p $WORKSPACE
           cd $WORKSPACE
+          # Clean existing workspace to avoid conflicts
+          rm -rf /opt/gbo/data/botserver
           # Update or clone botlib (preserve git history for sccache fingerprints)
           if [ -d botlib/.git ]; then
             git -C botlib pull origin main